Foreign Minister Angelino Alfano described the air strikes, carried out in response to a suspected chemical attack, as a "proportionate response in time and manner" which would act as a deterrent against further chemical attacks.
However, two of the main Italian oppostion parties - both of which have previously shown support for the American leader - appeared to distance themselves from Trump on Friday morning with comments condemning the missile strikes.
Northern League leader Matteo Salvini said Trump's decision was a "bad idea, big mistake, and a gift to Isis".
"Haven't the disasters in Iraq, Afghanistan and Libya taught them [the US administration] anything?" he asked, writing on his Facebook page.
Meanwhile, the Five Star Movement said the attacks were "likely to constitute a clear violation of international law" and added: "After 20 years of mistakes, it seems that nothing has changed, unfortunately."
Leader Beppe Grillo had on Thursday called for an immediate UN investigation into the apparent chemical attack on Syria, and the note on Friday criticized the US administration for "preferring to bomb before the independent inquiry."
"The solution to war cannot be another war," the party said.
Friday's criticism was a contrast to previous shows of support for Trump from both parties. In November, Salvini posted a series of jubilant tweets celebrating Trump's victory in the US elections, saying "Americans, thank you, thank you and thank you!"
He has previously hailed Trump as "heroic", and shared photos of the pair grinning and doing a thumbs-up sign together. However, Trump snubbed the far-right leader following the meeting, saying: "I didn't want to meet him, I don't even know him".
Five Star Movement leader Beppe Grillo did not formally endorse Trump, but praised him on his victory in a blogpost saying that it represented a "fuck you" to the establishment.
Elsewhere in Europe, France's far-right presidential candidate Marine Le Pen also said she "strongly condemned" the strikes on Syria.
And the French President Francois Hollande issued a joint statement with German Chancellor Angela Merkel, saying that Syrian President Bashar al-Assad bore "sole responsibility" for the US strike.